Make sure that your email client application is compatible for use with FileMaker. YOu can look up Send Mail in FileMaker Help to get the details.
If you dont' have an installer, you need to get one ASAP--even if this turns out not to be necessary to resolve this issue. What will you do if your computer is stolen or irreprably damaged?
If you registered your software, contact Filemaker Tech support and ask them for a new download link. Download the installer file and store multiple copies of the application in multiple locations--a flash drive makes a good choice for this and you can even toss one into a safe deposit box for safe keeping.
Yup, my email client wasn't compatible. When I switched to the supported Apple Mail client, it worked fine.
Currently downloading another copy of Filemaker for safekeeping!!